Soot and Sweat

Furnace workers performed dangerous, dirty, and difficult labor under the constant threat of a major explosion. To put the furnace in blast, workers first built a coal fire in the bottom of the crucible to evaporate moisture and preheat the furnace. Fillers then dumped washed coal, iron ore, and crushed marble stone through a charging hole at the top, with each mixture known as a charge. Producing pig iron depended on experienced workers using the correct proportions of ingredients; a general rule held that 365 bushels of coal, 4 tons of iron ore, and 3 tons of marble stone yielded 1 ton of pig iron. As charges melted in the crucible, more layers were added, and when the coal burned at temperatures of 3000 degrees, the iron ore and marble melted and impurities dissolved into the molten marble to form slag. Because slag was lighter than iron, it floated above the heavier molten iron and was drained from an opening at the furnace base. Pig iron bars could then be transported to market or sent to foundries for casting or to refinery forges for conversion into wrought iron. As demand for iron and then steel grew in the 19th century, pig iron became the foundation of the iron industry. By 1850, 25,000 ironworkers produced 500,00 tons of pig iron with a market value of $12,489,077. In 1855, the Oregon Ridge Furnace produced an award-winning 4,500 tons of pig iron with a profit value of $227,475, but rising production costs and failure to keep pace with new furnace technology led to its closure in 1857, after which the furnace was dismantled and its infrastructure sold.

Maryland · United States